Mounting arrangement for light emitting diodes

ABSTRACT

A modular light emitting diode (LED) mounting configuration is provided including a light source module having a plurality of pre-packaged LEDs arranged in a serial array. The module includes a heat conductive body portion adapted to conduct heat generated by the LEDs to an adjacent heat sink. As a result, the LEDs are able to be operated with a higher current than normally allowed. Thus, brightness and performance of the LEDs is increased without decreasing the life expectancy of the LEDs. The LED modules can be used in a variety of illumination applications employing one or more modules.

RELATED APPLICATIONS

[0001] This application is a continuation of copending U.S. applicationSer. No. 09/693,548, which was filed on Oct. 19, 2000, and which claimspriority to U.S. Provisional Patent Application No. 60/160,480, whichwas filed on Oct. 19, 1999 and U.S. Provisional Patent Application No.60/200,351, which was filed on Apr. 27, 2000. The entirety of each ofthese related applications is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is in the field of light emitting diode(LED) lighting devices and more particularly in the field of an LEDlighting module having heat transfer properties that improve theefficiency and performance of LEDs.

[0004] 2. Description of the Related Art

[0005] Light emitting diodes (LEDs) are currently used for a variety ofapplications. The compactness, efficiency and long life of LEDs isparticularly desirable and makes LEDs well suited for many applications.However, a limitation of LEDs is that they typically cannot maintain along-term brightness that is acceptable for middle to large-scaleillumination applications. Instead, more traditional incandescent orgas-filled light bulbs are often used.

[0006] An increase of the electrical current supplied to an LEDgenerally increases the brightness of the light emitted by the LED.However, increased current also increases the junction temperature ofthe LED. Increased juncture temperature may reduce the efficiency andthe lifetime of the LED. For example, it has been noted that for every10° C. increase in temperature, silicone and gallium arsenide lifetimedrops by a factor of 2.5-3. LEDs are often constructed of semiconductormaterials that share many similar properties with silicone and galliumarsenide.

SUMMARY OF THE INVENTION

[0007] Accordingly, there is a need in the art for an LED lightingapparatus having heat removal properties that allow an LED on theapparatus to operate at relatively high current levels withoutincreasing the juncture temperature of the LED beyond desired levels.

[0008] In accordance with an aspect of the present invention, an LEDmodule is provided for mounting on a heat conducting surface that issubstantially larger than the module. The module comprises a pluralityof LED packages and a circuit board. Each LED package has an LED and atleast one lead. The circuit board comprises a thin dielectric sheet anda plurality of electrically-conductive contacts on a first side of thedielectric sheet. Each of the contacts is configured to mount a lead ofan LED package such that the LEDs are connected in series. A heatconductive plate is disposed on a second side of the dielectric sheet.The plate has a first side which is in thermal communication with thecontacts through the dielectric sheet. The first side of the plate has asurface area substantially larger than a contact area between thecontacts and the dielectric sheet. The plate has a second side adaptedto provide thermal contact with the heat conducting surface. In thismanner, heat is transferred from the module to the heat conductingsurface.

[0009] In accordance with another aspect of the present invention, amodular lighting apparatus is provided for conducting heat away from alight source of the apparatus. The apparatus comprises a plurality ofLEDs and a circuit board. The circuit board has a main body and aplurality of electrically conductive contacts. Each of the LEDselectrically communicates with at least one of the contacts in a mannerso that the LEDs are configured in a series array. Each of the LEDselectrically communicates with corresponding contacts at an attachmentarea defined on each contact. An overall surface of the contact issubstantially larger than the attachment area. The plurality of contactsare arranged adjacent a first side of the main body and are in thermalcommunication with the first side of the main body. The main bodyelectrically insulates the plurality of contacts relative to oneanother.

[0010] For purposes of summarizing the invention and the advantagesachieved over the prior art, certain objects and advantages of theinvention have been described herein above. Of course, it is to beunderstood that not necessarily all such objects or advantages may beachieved in accordance with any particular embodiment of the invention.Thus, for example, those skilled in the art will recognize that theinvention may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

[0011] All of these embodiments are intended to be within the scope ofthe invention herein disclosed. These and other embodiments of thepresent invention will become readily apparent to those skilled in theart from the following detailed description of the preferred embodimentshaving reference to the attached figures, the invention not beinglimited to any particular preferred embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a perspective view of an LED module having features inaccordance with the present invention.

[0013]FIG. 2 is a schematic side view of a typical pre-packaged LEDlamp.

[0014]FIG. 3 is a top plan view of the LED module of FIG. 1.

[0015]FIG. 4 is a side plan view of the apparatus of FIG. 3.

[0016]FIG. 5 is a close-up side view of the apparatus of FIG. 3 mountedon a heat conductive member.

[0017]FIG. 6 is another sectional side view of the apparatus of FIG. 3mounted onto a heat conductive flat surface.

[0018]FIG. 7 is a side plan view of an LED module having features inaccordance with another embodiment of the present invention.

[0019]FIG. 8 is a side plan view of another LED module having featuresin accordance with yet another embodiment of the present invention.

[0020]FIG. 9 is a perspective view of an illumination apparatus havingfeatures in accordance with the present invention.

[0021]FIG. 10 is a side view of the apparatus of FIG. 9.

[0022]FIG. 11 is a bottom view of the apparatus of FIG. 9.

[0023]FIG. 12 is a top view of the apparatus of FIG. 9.

[0024]FIG. 13 is a schematic view of the apparatus of FIG. 9 mounted ona theater seat row end.

[0025]FIG. 14 is a side view of the apparatus of FIG. 13 showing themounting orientation.

[0026]FIG. 15 is a side view of a mounting barb.

[0027]FIG. 16 is a front plan view of the illumination apparatus of FIG.9.

[0028]FIG. 17 is a cutaway side plan view of the apparatus of FIG. 20.

[0029]FIG. 18 is a schematic plan view of a heat sink base plate.

[0030]FIG. 19 is a close-up side sectional view of an LED module mountedon a mount tab of a base plate.

[0031]FIG. 20 is a plan view of a lens for use with the apparatus ofFIG. 9.

[0032]FIG. 21 is a perspective view of a channel illumination apparatusincorporating LED modules having features in accordance with the presentinvention.

[0033]FIG. 22 is a close-up side view of an LED module mounted on amount tab.

[0034]FIG. 23 is a partial view of a wall of the apparatus of FIG. 21,taken along line 23-23.

[0035]FIG. 24 is a top view of an LED module mounted to a wall of theapparatus of FIG. 21.

[0036]FIG. 25 is a top view of an alternative embodiment of an LEDmodule mounted to a wall of the apparatus of FIG. 21.

[0037]FIG. 26A is a side view of an alternative embodiment of a lightingmodule being mounted onto a channel illumination apparatus wall member.

[0038]FIG. 26B shows the apparatus of the arrangement of FIG. 26A withthe lighting module installed.

[0039]FIG. 26C shows the arrangement of FIG. 26B with a lens installedon the wall member.

[0040]FIG. 26D shows a side view of an alternative embodiment of alighting module installed on a channel illumination apparatus wallmember.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0041] With reference first to FIG. 1, an embodiment of a light-emittingdiode (LED) lighting module 30 is disclosed. In the illustratedembodiment, the LED module 30 includes five pre-packaged LEDs 32arranged on one side of the module 30. It is to be understood, however,that LED modules having features in accordance with the presentinvention can be constructed having any number of LEDs 32 mounted in anydesired configuration.

[0042] With next reference to FIG. 2, a typical pre-packaged LED 32includes a diode chip 34 encased within a resin body 36. The body 36typically has a focusing lens portion 38. A negative lead 40 connects toan anode side 42 of the diode chip 34 and a positive lead 44 connects toa cathode side 46 of the diode chip 34. The positive lead 44 preferablyincludes a reflector portion 48 to help direct light from the diode 34to the lens portion 38.

[0043] With next reference to FIGS. 1-5, the LED module 30 preferablycomprises the five pre-packaged LED lamps 32 mounted in a linear arrayon a circuit board 50 and electrically connected in series. Theillustrated embodiment employs pre-packaged aluminum indium galliumphosphide (AlInGaP) LED lamps 32 such as model HLMT-PL00, which isavailable from Hewlett Packard. In the illustrated embodiment, each ofthe pre-packaged LEDs is substantially identical so that they emit thesame color of light. It is to be understood, however, that nonidenticalLEDs may be used to achieve certain desired lighting effects.

[0044] The illustrated circuit board 50 preferably is about 0.05 inchesthick, 1 inch long and 0.5 inch wide. It includes three layers: a coppercontact layer 52, an epoxy dielectric layer 54 and an aluminum main bodylayer 56. The copper contact layer 52 is made up of a series of sixelongate and generally parallel flat copper plates 60 that are adaptedto attach to the leads 40, 44 of the LEDs 32. Each of the coppercontacts 60 is electrically insulated from the other copper contacts 60by the dielectric layer 54. Preferably, the copper contacts 60 aresubstantially coplanar.

[0045] The pre-packaged LEDs 32 are attached to one side of the circuitboard 50, with the body portion 36 of each LED generally abutting a sideof the circuit board 50. The LED lens portion 38 is thus pointedoutwardly so as to direct light in a direction substantially coplanarwith the circuit board 50. The LED leads 40, 44 are soldered onto thecontacts 60 in order to create a series array of LEDs. Excess materialfrom the leads of the individual pre-packaged LED lamps may be removed,if desired. Each of the contacts 60, except for the first and lastcontact 62, 64, have both a negative lead 40 and a positive lead 44attached thereto. One of the first and last contacts 62, 64 has only anegative lead 40 attached thereto; the other has only a positive lead 44attached thereto.

[0046] A bonding area of the contacts accommodates the leads 40, 44,which are preferably bonded to the contact 60 with solder 68; however,each contact 60 preferably has a surface area much larger than isrequired for adequate bonding in the bonding area 66. The enlargedcontact surface area allows each contact 60 to operate as a heat sink,efficiently absorbing heat from the LED leads 40, 44. To maximize thisrole, the contacts 60 are shaped to be as large as possible while stillfitting upon the circuit board 50.

[0047] The dielectric layer 54 preferably has strong electricalinsulation properties but also relatively high heat conductanceproperties. In the illustrated embodiment, the layer 54 is preferably asthin as practicable. For example in the illustrated embodiment, thedielectric layer 54 comprises a layer of Thermagon® epoxy about 0.002inches thick.

[0048] It is to be understood that various materials and thicknesses canbe used for the dielectric layer 54. Generally, the lower the thermalconductivity of the material used for the dielectric layer, the thinnerthat dielectric layer should be in order to maximize heat transferproperties of the module. For example, in the illustrated embodiment,the layer of epoxy is very thin. Certain ceramic materials, such asberyllium oxide and aluminum nitride, are electrically non-conductivebut highly thermally conductive. When the dielectric layer isconstructed of such materials, it is not as crucial for the dielectriclayer to be so very thin, because of the high thermal conductivity ofthe material.

[0049] In the illustrated embodiment, the main body 56 makes up the bulkof the thickness of the circuit board 50 and preferably comprises a flataluminum plate. As with each of the individual contacts 60, the mainbody 56 functions as a heat conduit, absorbing heat from the contacts 60through the dielectric layer 54 to conduct heat away from the LEDs 32.However, rather than just absorbing heat from a single LED 32, the mainbody 56 acts as a common heat conduit, absorbing heat from all of thecontacts 60. As such, in the illustrated embodiment, the surface area ofthe main body 56 is about the same as the combined surface area of allof the individual contacts 60. The main body 56 can be significantlylarger than shown in the illustrated embodiment, but its relativelycompact shape is preferable in order to increase versatility whenmounting the light module 30. Additionally, the main body 56 isrelatively rigid and provides structural support for the lighting module30.

[0050] In the illustrated embodiment, aluminum has been chosen for itshigh thermal conductance properties and ease of manufacture. It is to beunderstood, however, that any material having advantageous thermalconductance properties, such as having thermal conductivity greater thanabout 100 watts per meter per Kelvin (W/m-K), would be acceptable.

[0051] A pair of holes 70 are preferably formed through the circuitboard 50 and are adapted to accommodate a pair of aluminum pop rivets72. The pop rivets 72 hold the circuit board 50 securely onto a heatconductive mount member 76. The mount member 76 functions as orcommunicates with a heat sink. Thus, heat from the LEDs 32 is conductedwith relatively little resistance through the module 30 to the attachedheat sink 76 so that the junction temperature of the diode chip 34within the LED 32 does not exceed a maximum desired level.

[0052] With reference again to FIGS. 3 and 5, a power supply wire 78 isattached across the first and last contacts 62, 64 of the circuit board50 so that electrical current is provided to the series-connected LEDs32. The power supply is preferably a 12-volt system and may be AC, DC orany other suitable power supply. A 12-volt AC system may be fullyrectified.

[0053] The small size of the LED module 30 provides versatility so thatmodules can be mounted at various places and in various configurations.For instance, some applications will include only a single module for aparticular lighting application, while other lighting applications willemploy a plurality of modules electrically connected in parallelrelative to each other.

[0054] It is also to be understood that any number of LEDs can beincluded in one module. For example, some modules may use two LEDs,while other modules may use 10 or more LEDs. One manner of determiningthe number of LEDs to include in a single module is to first determinethe desired operating voltage of a single LED of the module and also thevoltage of the power supply. The number of LEDs desired for the moduleis then roughly equal to the voltage of the power supply divided by theoperating voltage of each of the LEDs.

[0055] The present invention rapidly conducts heat away from the diodechip 34 of each LED 32 so as to permit the LEDs 32 to be operated inregimes that exceed normal operating parameters of the pre-packaged LEDs32. In particular, the heat sinks allow the LED circuit to be driven ina continuous, non-pulsed manner at a higher long-term electrical currentthan is possible for typical LED mounting configurations. This operatingcurrent is substantially greater than manufacturer-recommended maximums.The optical emission of the LEDs at the higher current is also markedlygreater than at manufacturer-suggested maximum currents.

[0056] The heat transfer arrangement of the LED modules 30 is especiallyadvantageous for pre-packaged LEDs 32 having relatively small packagingand for single-diode LED lamps. For instance, the HLMT-PL00 model LEDlamps used in the illustrated embodiment employ only a single diode, butsince heat can be drawn efficiently from that single diode through theleads and circuit board and into the heat sink, the diode can be run ata higher current than such LEDs are traditionally operated. At such acurrent, the single-diode LED shines brighter than LED lamps that employtwo or more diodes and which are brighter than a single-diode lampduring traditional operation. Of course, pre-packaged LED lamps havingmultiple diodes can also be employed with the present invention. It isalso to be understood that the relatively small packaging of the modelHLMT-PL00 lamps aids in heat transfer by allowing the heat sink to beattached to the leads closer to the diode chip.

[0057] With next reference to FIG. 5, a first reflective layer 80 ispreferably attached immediately on top of the contacts 60 of the circuitboard 50 and is held in position by the rivets 72. The first reflector80 preferably extends outwardly beyond the LEDs 32. The reflectivematerial preferably comprises an electrically non-conductive film suchas visible mirror film available from 3M. A second reflective layer 82is preferably attached to the mount member 76 at a point immediatelyadjacent the LED lamps 32. The second strip 82 is preferably bonded tothe mount surface 76 using adhesive in a manner known in the art.

[0058] With reference also to FIG. 6, the first reflective strip 80 ispreferably bent so as to form a convex reflective trough about the LEDs32. The convex trough is adapted to direct light rays emitted by theLEDs 32 outward with a minimum of reflections between the reflectorstrips 80, 82. Additionally, light from the LEDs is limited to beingdirected in a specified general direction by the reflecting films 80,82. As also shown in FIG. 6, the circuit board 50 can be mounteddirectly to any mount surface 76.

[0059] In another embodiment, the aluminum main body portion 56 may beof reduced thickness or may be formed of a softer metal so that themodule 30 can be partially deformed by a user. In this manner, themodule 30 can be adjusted to fit onto various surfaces, whether they areflat or curved. By being able to adjust the fit of the module to thesurface, the shared contact surface between the main body and theadjacent heat sink is maximized, improving heat transfer properties.Additional embodiments can use fasteners other than rivets to hold themodule into place on the mount surface/heat sink material. Theseadditional fasteners can include any known fastening means such aswelding, heat conductive adhesives, and the like.

[0060] As discussed above, a number of materials may be used for thecircuit board portion of the LED module. With specific reference to FIG.7, another embodiment of an LED module 86 comprises a series ofelongate, flat contacts 88 similar to those described above withreference to FIG. 3. The contacts 88 are mounted directly onto the mainbody portion 89. The main body 89 comprises a rigid, substantially flatceramic plate. The ceramic plate makes up the bulk of the circuit boardand provides structural support for the contacts 88. Also, the ceramicplate has a surface area about the same as the combined surface area ofthe contacts. In this manner, the plate is large enough to providestructural support for the contacts 88 and conduct heat away from eachof the contacts 88, but is small enough to allow the module 86 to berelatively small and easy to work with. The ceramic plate 89 ispreferably electrically non-conductive but has high heat conductivity.Thus, the contacts 88 are electrically insulated relative to each other,but heat from the contacts 88 is readily transferred to the ceramicplate 89 and into an adjoining heat sink.

[0061] With next reference to FIG. 8, another embodiment of an LEDlighting module 90 is shown. The LED module 90 comprises a circuit board92 having features substantially similar to the circuit board 50described above with reference to FIG. 3. The diode portion 94 of theLED 96 is mounted substantially directly onto the contacts 60 of thelighting module 90. In this manner, any thermal resistance from leads ofpre-packaged LEDs is eliminated by transferring heat directly from thediode 94 onto each heat sink contact 60, from which the heat isconducted to the main body 56 and then out of the module 90. In thisconfiguration, heat transfer properties are yet further improved.

[0062] As discussed above, an LED module having features as describedabove can be used in many applications such as, for example, indoor andoutdoor decorative lighting, commercial lighting, spot lighting, andeven room lighting. With next reference to FIGS. 9-12, a self-containedlighting apparatus 100 incorporates an LED module 30 and can be used inmany such applications. In the illustrated embodiment, the lightingapparatus 100 is adapted to be installed on the side of a row of theaterseats 102, as shown in FIG. 13, and is adapted to illuminate an aisle104 next to the theater seats 102.

[0063] The self-contained lighting apparatus 100 comprises a base plate106, a housing 108, and an LED module 30 arranged within the housing108. As shown in FIGS. 9, 10 and 13, the base plate 106 is preferablysubstantially circular and has a diameter of about 5.75 inches. The baseplate 106 is preferably formed of {fraction (1/16)}′ inch thick aluminumsheet. As described in more detail below, the plate functions as a heatsink to absorb and dissipate heat from the LED module. As such, the baseplate 106 is preferably formed as large as is practicable, givenaesthetic and installation concerns.

[0064] As discussed above, the lighting apparatus 100 is especiallyadapted to be mounted on an end panel 110 of a row of theater chairs 102in order to illuminate an adjacent aisle 104. As shown in FIGS. 13 and14, the base plate 106 is preferably installed in a verticalorientation. Such vertical orientation aids conductive heat transferfrom the base plate 106 to the environment.

[0065] The base plate 106 includes three holes 112 adapted to facilitatemounting. A ratcheting barb 116 (see FIG. 15) secures the plate 106 tothe panel 110. The barb 116 has an elongate main body 118 having aplurality of biased ribs 120 and terminating at a domed top 122.

[0066] To mount the apparatus on the end panel 110, a hole is firstformed in the end panel surface on which the apparatus is to be mounted.The base plate holes 112 are aligned with mount surface holes and thebarbs 116 are inserted through the base plate 106 into the holes. Theribs 120 prevent the barbs 116 from being drawn out of the holes onceinserted. Thus, the apparatus is securely held in place and cannot beeasily removed. The barbs 116 are especially advantageous because theyenable the device to be mounted on various surfaces. For example, thebarbs will securely mount the illumination apparatus on wooden or fabricsurfaces.

[0067] With reference next to FIGS. 16-19, a mount tab 130 is providedas an integral part of the base plate 106. The mounting tab 130 isadapted to receive an LED module 30 mounted thereon. The tab 30 ispreferably plastically deformed along a hinge line 132 to an angle θbetween about 20-45° relative to the main body 134 of the base plate106. More preferably, the mounting tab 130 is bent at an angle θ ofabout 33°. The inclusion of the tab 130 as an integral part of the baseplate 106 facilitates heat transfer from the tab 130 to the main body134 of the base plate. It is to be understood that the angle θ of thetab 130 relative to the base plate body 134 can be any desired angle asappropriate for the particular application of the lighting apparatus100.

[0068] A cut out portion 136 of the base plate 106 is providedsurrounding the mount tab 130. The cut out portion 136 provides spacefor components of the mount tab 130 to fit onto the base plate 106.Also, the cut out portion 136 helps define the shape of the mount tab130. As discussed above, the mount tab 130 is preferably plasticallydeformed along the hinge line 132. The length of the hinge line 132 isdetermined by the shape of the cut out portion 136 in that area. Also, ahole 138 is preferably formed in the hinge line 132. The hole 138further facilitates plastic deformation along the hinge line 132.

[0069] Power for the light source assembly 100 is preferably providedthrough a power cord 78 that enters the apparatus 100 through a backside of the base plate 106. The cord 78 preferably includes two 18 AWGconductors surrounded by an insulating sheet. Preferably, the powersupply is in the low voltage range. For example, the power supply ispreferably a 12-volt alternating current power source. As depicted inFIG. 18, power is preferably first provided through a full wave ridgerectifier 140 which rectifies the alternating current in a manner knownin the art so that substantially all of the current range can be used bythe LED module 40. In the illustrated embodiment, the LEDs arepreferably not electrically connected to a current-limiting resistor.Thus, maximum light output can be achieved. It is to be understood,however, that resistors may be desirable in some embodiments to regulatecurrent. Supply wires 142 extend from the rectifier 140 and providerectified power to the LED module 30 mounted on the mounting tab 130.

[0070] With reference again to FIGS. 9-12, 16 and 17, the housing 108 ispositioned on the base plate 106 and preferably encloses the wiringconnections in the light source assembly 100. The housing 108 ispreferably substantially semi-spherical in shape and has a notch 144formed on the bottom side. A cavity 146 is formed through the notch 144and allows visual access to the light source assembly 100. A secondcavity 148 is formed on the top side and preferably includes a plug 150which may, if desired, include a marking such as a row number. In anadditional embodiment, a portion of the light from the LED module 30, oreven from an alternative light source, may provide light to light up theaisle marker.

[0071] The housing 108 is preferably secured to the base plate 106 by apair of screws 152. Preferably, the screws 152 extend throughcountersunk holes 154 in the base plate 106. This enables the base plate106 to be substantially flat on the back side, allowing the plate to bemounted flush with the mount surface. As shown in FIG. 17, threadedscrew receiver posts 156 are formed within the housing 108 and areadapted to accommodate the screw threads.

[0072] The LED module 30 is attached to the mount tab 130 by the poprivets 72. The module 30 and rivets 72 conduct heat from the LEDs 32 tothe mount tab 130. Since the tab 130 is integrally formed as a part ofthe base plate 106, heat flows freely from the tab 130 to the main body134 of the base plate. The base plate 106 has high heat conductanceproperties and a relatively large surface area, thus facilitatingefficient heat transfer to the environment and allowing the base plate106 to function as a heat sink.

[0073] As discussed above, the first reflective strip 80 of the LEDmodule 30 is preferably bent so as to form a convex trough about theLEDs. The second reflector strip 82 is attached to the base plate mounttab 130 at a point immediately adjacent the LED lamps 32. Thus, lightfrom the LEDs is collimated and directed out of the bottom cavity 146 ofthe housing 108, while minimizing the number of reflections the lightmust make between the reflectors (see FIG. 6). Such reflections may eachreduce the intensity of light reflected.

[0074] A lens or shield 160 is provided and is adapted to be positionedbetween the LEDs 32 and the environment outside of the housing cavity108. The shield 160 prevents direct access to the LEDs 32 and thusprevents harm that may occur from vandalism or the like, but alsotransmits light emitted by the light source 100.

[0075]FIG. 20 shows an embodiment of the shield 160 adapted for use inthe present invention. As shown, the shield 160 is substantiallylenticularly shaped and has a notch 162 formed on either end thereof.With reference back to FIG. 18, the mounting tab 130 of the base plate106 also has a pair of notches 164 formed therein.

[0076] As shown in FIG. 16, the lens/shield notches 162 are adapted tofit within the tab notches 164 so that the shield 160 is held in placein a substantially arcuate position. The shield thus, in effect, wrapsaround one side of the LEDs 32. When the shield 160 is wrapped aroundthe LEDs 32, the shield 160 contacts the first reflector film 80,deflecting the film 80 to further form the film in a convex arrangement.The shield 160 is preferably formed of a clear polycarbonate material,but it is to be understood that the shield 160 may be formed of anyclear or colored transmissive material as desired by the user.

[0077] The LED module 30 of the present invention can also be used inapplications using a plurality of such modules 30 to appropriately lighta lighting apparatus such as a channel illumination device. Channelillumination devices are frequently used for signage including bordersand lettering. In these devices, a wall structure outlines a desiredshape to be illuminated, with one or more channels defined between thewalls. A light source is mounted within the channel and a translucentdiffusing lens is usually arranged at the top edges of the walls so asto enclose the channel. In this manner, a desired shape can beilluminated in a desired color as defined by the color of the lens.

[0078] Typically, a gas-containing light source such as a neon light iscustom-shaped to fit within the channel. Although the diffusing lens isplaced over the light source, the light apparatus may still produce “hotspots,” which are portions of the sign that are visibly brighter thanother portions of the sign. Such hot spots result because the lightingapparatus shines directly at the lens, and the lens may have limitedlight-diffusing capability. Incandescent lamps may also be used toilluminate such a channel illumination apparatus; however, the hot spotproblem typically is even more pronounced with incandescent lights.

[0079] Both incandescent and gas-filled lights have relatively highmanufacturing and operation costs. For instance, gas-filled lightstypically require custom shaping and installation and therefore can bevery expensive to manufacture. Additionally, both incandescent andgas-filled lights have high power requirements.

[0080] With reference next to FIG. 21, an embodiment of a channelillumination apparatus 170 is disclosed comprising a casing 172 in theshape of a “P.” The casing 172 includes a plurality of walls 174 and abottom 176, which together define at least one channel. The surfaces ofthe walls 174 and bottom 176 are diffusely-reflective, preferably beingcoated with a flat white coating. The walls 174 are preferably formed ofa durable sturdy metal having relatively high heat conductivity. Aplurality of LED lighting modules 30 are mounted to the walls 174 of thecasing 172 in a spaced-apart manner. A translucent light-diffusing lens(not shown) is preferably disposed on a top edge 178 of the walls 174and encloses the channel.

[0081] With next reference to FIG. 22, the pop rivets 72 hold the LEDmodule 30 securely onto a heat conductive mount tab 180. The mount tab180, in turn, may be connected, by rivets 182 or any other fasteningmeans, to the walls 174 of the channel apparatus as shown in FIG. 23.Preferably, the connection of the mount tab 180 to the walls 174facilitates heat transfer from the tab 180 to the wall 174. The channelwall has a relatively large surface area, facilitating efficient heattransfer to the environment and enabling the channel wall 174 tofunction as a heat sink.

[0082] In additional embodiments, the casing 172 may be constructed ofmaterials, such as certain plastics, that may not be capable offunctioning as heat sinks because of inferior heat conductanceproperties. In such embodiments, the LED module 30 can be connected toits own relatively large heat sink base plate, which is mounted to thewall of the casing. An example of such a heat sink plate in conjunctionwith an LED lighting module has been disclosed above with reference tothe self-contained lighting apparatus 100.

[0083] With continued reference to FIGS. 22 and 23, the LED modules 30are preferably electrically connected in parallel relative to othermodules 30 in the illumination apparatus 170. A power supply cord 184preferably enters through a wall 174 or bottom surface 176 of the casing172 and preferably comprises two 18 AWG main conductors 186. Short wires188 are attached to the first and last contacts 62, 64 of each module 30and preferably connect with respective main conductors 186 usinginsulation displacement connectors (IDCs) 190 as shown in FIG. 23.

[0084] Although the LEDs 32 in the modules 30 are operated at currentshigher than typical LEDs, the power efficiency characteristic of LEDs isretained. For example, a typical channel light employing a neon-filledlight could be expected to use about 60 watts of power during operation.A corresponding channel illumination apparatus 170 using a plurality ofLED modules can be expected to use about 4.5 watts of power.

[0085] With reference again to FIG. 23, the LED modules 30 arepreferably positioned so that the LEDs 32 face generally downwardly,directing light away from the lens. The light is preferably directed tothe diffusely-reflective wall and bottom surfaces 174, 176 of the casing172. The hot spots associated with more direct forms of lighting, suchas typical incandescent and gas-filled bulb arrangements, are thusavoided.

[0086] The reflectors 80, 82 of the LED modules 30 aid in directinglight rays emanating from the LEDs toward the diffusely-reflectivesurfaces. It is to be understood, however, that an LED module 30 notemploying reflectors can also be appropriately used.

[0087] The relatively low profile of each LED module 30 facilitates theindirect method of lighting because substantially no shadow is createdby the module when it is positioned on the wall 174. A higher-profilelight module would cast a shadow on the lens, producing an undesirable,visibly darkened area. To minimize the potential of shadowing, it isdesired to space the modules 30 and accompanying power wires 186, 188 adistance of at least about 1/2 inch from the top edge 178 of the wall174. More preferably, the modules 30 are spaced more than one inch fromthe top 178 of the wall 174.

[0088] The small size and low profile of the LED modules 30 enables themodules to be mounted at various places along the channel wall 174. Forinstance, with reference to FIGS. 21 and 24, light modules 30 mustsometimes be mounted to curving portions 192 of walls 174. The modules30 are preferably about 1 inch to 1-½ inch long, including the mountingtab 180, and thus can be acceptably mounted to a curving wall 192. Asshown, the mounting tab 180 may be separated from the curving wall 192along a portion of its length, but the module is small enough that it issuitable for riveting to the wall.

[0089] In an additional embodiment shown in FIG. 25, the module 30comprises the circuit board without the mount tab 180. In such anembodiment, the circuit board 50 may be mounted directly to the wall,having an even better fit relative to the curved surface 192 than theembodiment using a mount tab. In still another embodiment, the LEDmodule's main body 56 is formed of a bendable material, which allows themodule to fit more closely and easily to the curved wall surface.

[0090] Although the LED modules 30 disclosed above are mounted to thechannel casing wall 174 with rivets 182, it is to be understood that anymethod of mounting may be acceptably used. With reference next to FIGS.26A-C, an additional embodiment comprises an LED module 30 mounted to amounting tab 200 which comprises an elongate body portion 202 and a clipportion 204. The clip portion 204 is urged over the top edge 178 of thecasing wall 172, firmly holding the mounting tab 200 to the wall 174 asshown in FIG. 26B. The lens 206 preferably has a channel portion 208which is adapted to engage the top edge 178 of the casing wall 174 andcan be fit over the clip portion 204 of the mount tab 200 as shown inFIGS. 26B and 26C. This mounting arrangement is simple and providesample surface area contact between the casing wall 174 and the mountingtab 200 so that heat transfer is facilitated.

[0091] In the embodiment shown in FIG. 21, the casing walls 174 areabout 3 to 4 inches deep and the width of the channel is about 3 to 4inches between the walls. In an apparatus of this size, LED modules 30positioned on one side of the channel can provide sufficient lighting.The modules are preferably spaced about 5-6 inches apart. As may beanticipated, larger channel apparatus will likely require somewhatdifferent arrangements of LED modules, including employing more LEDmodules. For example, a channel illumination apparatus having a channelwidth of 1 to 2 feet may employ LED modules on both walls and may evenuse multiple rows of LED modules. Additionally, the orientation of eachof the modules may be varied in such a large channel illuminationapparatus. For instance, with reference to FIG. 26D, some of the LEDmodules may desirably be angled so as to direct light at various anglesrelative to the diffusely reflective surfaces.

[0092] In order to avoid creating hot spots, a direct light path fromthe LED 32 to the lens 206 is preferably avoided. However, it is to beunderstood that pre-packaged LED lamps 32 having diffusely-reflectivelenses may advantageously be directed toward the channel letter lens206.

[0093] Using LED modules 30 to illuminate a channel illuminationapparatus 170 provides significant savings during manufacturing. Forexample, a number of LED modules, along with appropriate wiring andhardware, can be included in a kit which allows a technician to easilyassemble a light by simply securing the modules in place along the wallof the casing and connecting the wiring appropriately using the IDCs.Although rivet holes may have to be drilled through the wall, there isno need for custom shaping, as is required with gas-filled bulbs.Accordingly, manufacturing effort and costs are significantly reduced.

[0094] Individual LEDs emit generally monochromatic light. Thus, it ispreferable that an LED type be chosen which corresponds to the desiredillumination color. Additionally, the diffuser is preferably chosen tobe substantially the same color as the LEDs. Such an arrangementfacilitates desirable brightness and color results. It is also to beunderstood that the diffusely-reflective wall and bottom surfaces mayadvantageously be coated to match the desired illumination color.

[0095] Although this invention has been disclosed in the context ofcertain preferred embodiments and examples, it will be understood bythose skilled in the art that the present invention extends beyond thespecifically-disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications and equivalentsthereof. In addition, while a number of variations of the invention havebeen shown and described in detail, other modifications, which arewithin the scope of this invention, will be readily apparent to those ofskill in the art based upon this disclosure. It is also contemplatedthat various combinations or subcombinations of the specific featuresand aspects of the embodiments may be made and still fall within thescope of the invention. Accordingly, it should be understood thatvarious features and aspects of the disclosed embodiments can becombined with or substituted for one another in order to form varyingmodes of the disclosed invention. Thus, it is intended that the scope ofthe present invention herein disclosed should not be limited by theparticular disclosed embodiments described above, but should bedetermined only by a fair reading of the claims that follow.

What is claimed is:
 1. An illumination system, comprising: at least onechannel defined by a plurality of wall surfaces and a back surface; atranslucent diffuser extending over the channel; and a plurality oflight emitting diode (LED) modules disposed within the channel andattached to at least one of the channel surfaces, the LED modules beingelectrically connected to one another in parallel, each of the LEDmodules comprising: a plurality of LEDs; a circuit board comprising adielectric portion, the LEDs disposed on a first side of the dielectricportion and arranged such that the plurality of LEDs are electricallyconnected in series; and a heat conductive metal on a second side of thedielectric portion, which heat conductive metal draws LED-generated heatfrom the first side for dissipation in the channel.